Crystalline dihydroxy phenols



Patented `Mar. 15, 1949 `UNITED CRYSTALLIN E DIHYDROXY PHENOLS Huwara L.Bender, Alford G. Farnham', and John W. Guyer, Bloomfield, Nr J.,assignors to Banellte Corporation, a corporation ofNew JerseyApplication March 24, 1944, Serial No. 527,988

8 Claims. (Cl. 260-619) This invention comprises the phenols orcrystalline hydroxy-hydroxy'-diphenyl-methanes and related compounds,and of interest because of their resin-forming properties. Of the sixisomeric methanes, Beilstein (VI, 994-999) gives methods for thepreparation of the '2,4, the 3,3' and the 4,4; Iorthe 2,2' onlybrominated and nitrated compounds are listed, and there are noreferences of any kind to the 2,3' and the 3,4 iso'- mers. The 2,4'compound is described as obtained in the form of needles melting at117-118 C., and the 4,4' compound is said to occur in the form of platesor. needles with a melting point of 158 C. Apart from Beilstein, thereare records of attempts at producing the 2,2' compound that express theconclusion that the compound cannot exist as such but only in the formof xanthene because of the elimination of water between the hydroxylgroups (J. S. C. Ind., 49, 252; 58,

It has' now been found that the literature reierences are incorrect,both as to the production hitherto of pure isomers of the 2,4' and 4,4'type and as to the inability of producing the 2,2' type of isomer. Whatis more, all six dihydroxy diphenyl-methanes (including the 2,3' and the3,4' isomers not mentioned by Beilstein) have now been isolated as'purecrystals with melting points as follows:

@QO, C. l

hydes and ketones result By the foregoing terminology it is to beunderstood that 2 designates an ortho position on one ring and 2' theortho position on the other ring of the diphenyl methane; 2 and 2' aretherefore also inclusive of 6 and 6'. Likewise 3 and 3' des-- tended tocondensed chains having multiple pointsv of connection per ring. Thepositions are graphically represented as follows:

H C if@ The six isomers, here under consideration as phenols and thatcan be reacted further to form 3l v 2l 415, 6,11

lresins, are basically two ring compounds, but by reaction withformaldehyde or equivalent they produce intermediates consisting ofchains of 4, 6, 8 or any multiple of the two rings, and these chains canbe cross-linked by a hardening agent to give the infusible orheat-hardened resins; chains can also be produced with an odd number ofrings by including phenol, monohydroxy benzene, as a reactant. When inthe reaction formaldehyde is replaced by other carbonyl organiccompounds selected. from the class consisting of aldehydes and ketonesand derivatives engendering them, such as acetaldehyde, benzaldehyde,acetone, hexamethylenetetrarnine, etc., the aldein corresponding changesin the methylene groups providing the methylene chain linkages;Isubstituted phenols provide corresponding substitutions on the phenylrings of the chain. These substitution products and derivatives areherein included as diphenylolmethanes.

The reaction data indicate that the six methanes here underconsideration fall into two groups: group I including the 2,2', 2,4'and-the 4,4' isomers, and group II the 2,3', 3,3 and 3.4' isomers.

In the reaction of phenolwith formaldehyde, the substitution tends to gorst to the ortho position on the phenol ring to form a methylol groupwhich in turn reacts with a second phenol to give thediphenylol-methane; the next positions on the ring in the order ofreactivity are the para and the remaining ortho positions. The isomersof group I accordingly can form vby the direct reaction of phenol andformaldehyde under proper reacting conditions, and these methanes inturn can react with more formaldehyde, or with the splitting oir ofwater can react with formaldehyde from the direct reaction oi' phenoland formaldeand any other phenol, to produce resins consisthyde),because conditions areas yet not known ing of multiple orthoorpara-methylene-chainunder which the methylene will directly unite in edphenols. In such resin chains, the open posithe meta positions. Group IImethanes are partions (of the three reactive positions ortho, orthoticularly differentiated in that substitution in the and para t0 thehydroxyl) are generally ortho meta position results in a methane asreactive or and occasionally para, and these are available for more sothan phenol itself; for instance phenol cross-linkage between chains toproduce the heatreacts with by .weight of hexamethylcnereactive orhardening resins. The 4,4 isomers tetramine at 160 C. to an infusiblegel in 165 when united by formaldehyde seem to t particu- 1o seconds,but with the same molar methylene ratio larly well into a chainformation, due to the hythe 3,3' isomer reacts 1.120 seconds, the 2,3' mdrogen-bOnding energy (I) 0f` the hydroxyl .140 seconds, and the 3,4isomer in 130 seconds groups, to leave only ortho (o) positions open asto infusible gels. As thevmeta substitution leaves expressed by thestructural formulerfor a chain: openl in each ring of the diphenylolmethane the i i i i i "capirne-- mo oH":Ho on=no on:

The 2,4' isomer cannot hydrogen-bond as well as three reactive ortho,ortho and para positions in the 4.4' and on test it was found to beslower in the isomers, the isomers of group II are desirable, reactionwith formaldehyde; it is indicated .by even though diflicult tomanufacture and expenthe structural chain formula: sive, forrapid-reacting and high cross-linking 'I'he 2,2' isomer when united byformaldehyde resin chains as evidenced by the structural shows a stillmore difllcult condition for forming formula:

0H Ho oli Ho 0E (o) (o) fi@ lo) (o) Q (o) (o) H H H t/ 5/ (p) i (D.) (D)(p) (D) I (D) hydrogen-bonded rings; but it does leave the more It canbe appreciated from this that even an active para (p) positions open togive it increased occasional residue of the meta structure in a speed ofcross-bonding reaction, as shown by the mixture adds materially to thecross-bonding restructural chain formula: activityof the composition; incomparison with iZI-O-m The reaction speeds of the pure isomers with 15a group I isomer, the meta. structure' has twice the per cent by weightof hexamethylenetetramine at number of reactive positions available. C.to the infusible gel stage have been deter- With respect to the reactionspeeds with 15% mined as follows: 2,4' isomer,'240 seconds; 4,4' ofhexamethylenetetramine given in the foreisomer, seconds; 2,2' isomer, 60seconds. The 65 going, it is to be observed that the isomers, with factsaccordingly appear to support the ortho, the exception of the2.2isomer,fall intoadeinite para and hydrogen-bonding theory explainedin pattern: the foregoing. The addition of methylene to thehydroxyphenyl ring at an ortho or para position, however,- 70

2,3 isomer-140 seconds reduces the reactivity to a corresponding extent,

. 3,4 isomer-130 seconds and in this respect the group II methanesessen- 3 3, is0mer 120 Seconds tially differ from the group I methanes.So far, the group II methanes (2,3'; 3,3; 3,4) have only The 2,2 is,however, an outstanding exception been made by indirect methods (asdistinguished 75 with a speed of 60 seconds, and this is of impor- Ytance since its inclusion in a composition offers a means forcontrolling or accelerating hardening speeds of other isomers orresins.` In a further respect it differs most markedly in that theisomer in the infusible state is flexible and elastic in the film formon tin plate; this property is believed to be actual bromine values forthe dihydroxy-diphenyl-methanes, and 'from these were calculated thebromine value per hydroxy-phenyl ring by subtracting the methylene valueand dividing by two. The actual determinations and calculated values areglvenin the following table:

suben Deter- 051mm D" Substance tuted mined DES per m01 om phenylmon-phenyl p-oH-pneny1 v Benzene 0 0.18 0 0 0 0 Phenol 1 4. 65 0 4.65 00 Diphenyl 2 l. 09 0 0. 545 0 0 Diphenyl-methan 2 2.13 1.04 0.545 0 02monohydroxydi hen l-methane.. 2 4.71 1 ,04 0.545 3.125 04,4dlhydroxydip eny -methane 2 10.11 1.04 0 0 U 4.542,4-dihydroxy-diphenyl-methene 2 8. 64 l. 04 0 3. 125 4. 542,2dihydroxy-diphenyl-methane 2 6. 40 0. 15 0 3. 125 0 due to a lessernumber of cross linkages taking place in the hardening or setting up ofthe isomer.

Characteristic of both groups of methanes is their crystalline structurewhich permits purification in a conventional manner, such asdistillation, crystallization from solvents, etc. and

thereby obtained free from all traces of unresf acted phenols,formaldehyde, catalysts, byproducts, etc. This is an advantage of utmostimportance in the\ phenolic resin field, for lt has been the reactantsand by-products remaining in the resinous form of reaction products thathave been found to be the sources of difficulty in controlling the resinproperties and in avoiding discoloration and the like; yet the purifiedproducts are found to be fully reactive with hardening agents likehexamethylenetetramine.

The properties obtained for the crystalline derivatives of theseisomeric materials were compared with the chemical literature, and mixedmelting points were made with authentic standards `where possible.Derivatives made and proven with their melting points are as follows:

The value for the para-hydroxy ring was calculated by subtracting theCH2 value and dividing by two. From the calculated values for the 2,4methane, the bromine value per mol is 8.70 which agrees very closelywith the actual determination.'

The methylene value for the 2,2 isomer, however, reduces to 0.15v inorder to make the calculated values (obtained from the bromine values ofthe other compounds) agree with the actually observed value of 6.40;there is an explanation for this on the hydrogen-bonding theory.

The 2,2 isomer as such can exist in the two forms:

no 0H oH1Ho (a) V(b) The form (b) having hydrogen-bonding favorsincreased reaction rate with formaldehyde to These derivatives wereinstrumental in checking the structural formulae assigned to theisomers. l

Pxoor or STRUCTURAL FoaMULAr:

In addition to the preparation of derivatives of known constitution thatserve as checks, the positions of the hydroxyls on the phenyl rings ofthe crystalline isomers of group I were determined by reacting` theselected isomer with potassium bromide-bromate under conditions leadingto the substitution of 5 bromine atoms on a ring. These conditions wereobtained by reacting phenol with an excess of potassium bromide-bromatefor two hours at C., and it was found the phenol united with 4.65bromine atoms. Pure reference materials-benzene, diphenyl, diphenylmethane and ortho hydroxy diphenyl methane were available and were usedto establish bromine values for the phenyl ring, the bonding methylene,and the ortho-monohydroxy-phenyl ring under the conditions establishedfor phenol. There were then obtained under these conditions the formchains, but the bonding interferes with the brominat on of the methylenegroup; chaining of the 2,2 isomer cannot further influence this factor,since the isomer itself has all its possible hydrogen bonding. Incomparison the 4,4' isomer in itself presents no possibility of hydrogenbonding, and it is therefore active to bromine; the chaining of the 4,4isomer, however, causes hydrogen-bonding and so a great reduction inbromine activity.

To demonstrate the foregoing and avoid crosslinking, a fusible resinchain of average low mo.. lecular weight (636) was made from the 2,2'isomer and a similar resin (molecular weight 627) was made from` the4,4' isomer by reaction with formaldehyde. From the preceding table, ifthere is no hydrogen-bonding, no added `methylenes or cross-linking, thecalculated bromne value for `the 2,2 chain per phenyl ring andconnecting methylene is (in the average chain formation there is onemethylene added for every two rings and thea The actual determined valuefor the 2,'2 resin chain was 16.17 per mol or 2.69 per ring plusmethylene, and that determined for the 4,4 resin chain was 18.25 per molor 3.04 per ring plus methylene. The value`6f 2.69 for a ring of the2,2' resin chain agrees closely with the calculated value oi 2.645, butthat of 3.04 for a ring of the 4,4' resin chain is a decided departurefrom the calculated value of 4.06. In the latter case there wasevidently a disturbance herein called hydrogenbonding.

Whatever the theory, however, the findings that products permittinghydrogen-bonding have an accelerated rate of reaction with hardener and4a retarded rate of bromination is of practical importance incontrolling resin reactions. In this connection it has been found thathigh crosslinking speed begins for resins that test at a brominationvalue of about 2.85 atoms per ring or approximately 2.23 grams ofbromine added to veach grain of resin, and that the reaction speedincreases as the bromination values become less. It has also beendiscovered that the high crosslinklng speeds are largely independent ofthe resin chain lengths; resins are thus obtainable that can pass from avery uid or high ow condition to infusible gels in a minute or less at160 C.

PURIrY DETERMINATION The purity of the isomers obtained was determinedby a method dependent upon solubility values and is illustratedy in theaccompanying drawing by a graph showing a series of straight line curvesplotted from data obtained by the method.

The procedure followed was that of addingl a sample in excess of theamount going into solution to benzene or other suitable solvent untilsaturated at a slightly elevated temperature and then allowing thesolution to come to equilibrium at 25 C. (10.1 C.). A portion wasfiltered free of excess solid and the amount in solution determined. Forany one impure sample an increased solubility was found to lie on astraight line curve obtained by plotting the solubllities for differentamounts of excess. For compositions, known to contain only two isomersbut in varying proportions, the plotting of the solubllities gave aseries of curves but all intersecting at one point;l the intersectionwas the value of the solubility of the major component. A pure materialgives the same solubility value for varying amounts of excess.

As an illustration the test for purity was applied to known mixtures ofthe 4,4 isomer with minor percentages of the 2,4 isomer. As shown by theplotted curves of the drawing, almost 0.0035 gram of a 50-50 mixturewent into solution per each gram of benzene, the solubility measure withthat amount being 0.00325 gram; increasing the solids added to 0.007gram, however, gave an increased solubility of about 0.0049 gram `and aiurther increase to 0.012 gram, indicated a solubility of over 0.007gram. The solubility determinations were repeated for a mixture of 66.7%of 4,4 and 33.3% oi' 2,4; a mixture of 75% 4,4 and 25% 2,4'; and mixtureof 95% 4,4' and 5% 2,4'. In each case a straight line curve wasobtained, and

it is to be observed that these lines intersect at a common point. Whenthe pure 4,4' was isolated, diilerent excess amounts of solute gave thesame solubility value of 0.001395i0.000001 gram per each gram ofbenzene; the straight line curve passed through the intersection of theother curves indicating a solubility of 0001401000005 gram per each gramof benzene. The pure product then is known when the solubility remainsthe same for varying amounts of excess, and this value corresponds tothe intersection of the straight line curves obtained from admixtureswith an impurity. The corrected melting point of the pure 4,4' productwas found to be 162.26" C., and the mixture containing 5% of 2,4 had amelting point of 157-158 C. or that heretofore assigned to the pure 4,4isomer.

GROUP lI Isomans 4,4-dihz/droy-diphenyl-methane The discovery made withregard to the impurity of the 4,4 isomer as described in the literatureis most surprising, for the isomer with a melting point of 158 C. hasbeen accepted as the pure 4,4` standard for many years and repeatedlyconfirmed by many workers in the field .(Beilstein, 6,' 995; Zincke,Ann., 302, 237 (1898); Lunjac, Chem. Centr., 1, 1650 (1905); Baekeland,Ind. Eng. Chem., 1, 149 (1909); Traubenburg, Z., angew, Chem., 36, -515(1923); Harden and Reid, J. A. C. S., 54, 4325 1932); Chem. RubberHandbook26th ed., 847 (1942)). The discovery came about in connectionwith the preparation of the 4,4 crystals for use as standards andobtained from diphenyl-methane by nitrating to p,pdiamino-diphenyl-methane and diazotizing the diamine-compound to4,4dihydroxydiphenyl methane with a melting point of 158 C. inaccordance with the literature. In rechecking for purity by the methoddependent upon excess so1- ute present in a solution, however, it wasfound that the product melting at 158 C. gave increased solubility asthe amount of excess solid was increased, and this indicated an impureproduct. It was then discovered that, under the purification conditionsof heat and solvent normally used, the product tended to revert to alower melting mixture; but by crystallizing the impure product at'roomtemperature from a solution in a mixture of toluene and butanol,followed by crystallization from pure toluene, a product was obtainedwith a melting point of 162-163 C., or more exactly 162.26 C. Thisproduct when tested by the method of excess solids in benzene solutiongave a constant solubility irrespective' of the amount of excess solidphase present, thus establlshing its purity.

The preparation of the 4,4 compound is disclosed by the followingexamples.

Example 1.-40 grams of diphenyl-methane were nitrated with excess nitricacid having a specic gravity of 1.42 at 50 C. The product was washedfree of vnitric acid, washed with ether, then dissolved in benzene, andcrystallized. Crystals of a melting point of 182-183.5 C. were obtainedin the amount of 12.1 grams. The product was purified4,4'dinitro-diphenyl-methane.

64.1 grams of the 4,4-dinitro-diphenyl-meth- 29 grams ofthe4.4'-diamino-dlphenyl-methane, boiling point 230-240 C. at 5 mm., wastreated with 21 grams NaNOa at 0 C. in the presence of 70 cc. H2SO4 andice. lThe product was .separated by ltratiom dissolved in NaOH andprecipitated by acid. The crystals were ltered oil and dried. They werepuried by distillation and melted at 158 C. Recrystallization from aseries of single solvents gave 3.6 grams with melting point of 158 C.

This supposed pure product was impure by the method of solubility withexcess solute present, and the residue from such solution was found tobe slightly higher in melting point. By crystallizing at roomtemperature the impure sample from a mixture of toluene-butanol followedby a crystallization from pure toluene, a yield of 2.6 grams of materialwas obtained with a melting point of 162-163 C. This when tested by themethod of excess solutes was pure and remained constant.

Example 2.-Large quantities of the material were then made by theprocedure of reacting phenol and formaldehyde in the presence of HC1catalyst, distilling the crystallizing fraction and recrystallizing tothe 162163C. purity material. The product was not depressed in meltingpoint when mixed with the above standard. Furthermore the crystals,melting point 162-163 C. and produced from phenol and formaldehyde, gavethe same solubility irrespective of excess solute used, namely .001395(1000001 gram) per 1.0000 gram benzene at 25 C.

The next problem was that of obtaining a proper standard for the 2,4compound. For this purpose diphenyl-methane was nitrated to the2,4'dinitro compound, and purified; it was reduced to the2,4'-diamino-diphenyl-methane which was diazotized to the dihydroxyproduct to yield crystals with a melting point of 116 C.A

Upon checking for purity, the crystals were found impure; but byextracting with a small amount of caustic and several recrystallizationsfrom alcohol, crystals with a melting point of 119120 C. were recoveredand were better than 99.5% pure by the excess solids method. Specificexamples follow.

Eample 3.100 grams diphenyl-methane, 100 grams concentrated H2SO4 and400 grams nitric acid having a density of 1.425, were held 24 hours at20-30 C. Poured into water, there was obtained 40 grams of a crude solidwith a melting point of 178-183 C. Recrystallization from benzene gave22 grams with a melting point of 182183.5 C., and the product was the4,4'- dinitro product.

The benzene mother liquor-was concentrated to yield 90.1 grams crude2,4dinitrodiphenyl methane. When recrystallized, 76 grams with a meltingpoint of 115-118 C. were obtained, and reduction with ironand aceticacid gave 35.7 grams of the 2,4'-diamino-dphenyl-methane with a meltingpoint of 86-88 C. The product was diazotized in a mixture of 95 cc.water and 70 cc. H2SO4, and the liquid obtained was washed with waterand distilled. When recrystallized at room temperature from benzene andbutanol the product had a melting point of 119-120 C. As a check, it wasmade into the diacetate and gave a material having a melting point ofExample 4.-In`the reaction of phenol an formaldehyde with HC1 ascatalyst, the distillation of the crystalline fraction obtained gave ayield of a distillate at 210215 C. and 2 mm. pressure from whichcrystals with a melting point of 119-120 C. were obtained from solutionin butyl alcohol. These crystals when mixed 7273.5 C., and this is thecorrect melting point with the above standard 2,4' isomer crystals gaveno depression of the melting point, thus establishing theml to be also2,4' isomer crystals. The solubility was 0008751.00005 gram per gram ofbenzene at 25 C.

2,2'-dihz/drory-diphenyl-methane From the washings and the mother liquorof the 2,4 material there were recovered some crystals with a meltingpoint of 119120" C. which when added to the pure 2,4' material de'pressed its melting point. The new material was found to be a pureisomer with the proper hydroxyl content and it was later determined tobe the missing 2,2' isomer.

Example 5 .--5 grams of the crystals with a melting point of 119-120 C.were heated at atmospheric pressure by placing the distilling ask in anoil bath heated to 350 C.` 3.8 grams of material were distilled througha short column leaving 1.1 grams of residue. The distillation point wasdetermined as 315320 C. with some change of the product. From thedistillate were isolated unchanged 2,2-dihydroxy-diphenyl-methane andsome caustic insoluble material. The latter was recrystallized to givecrystals melting at 102-103 C., and these, when mixed with a knownsample made from xanthene, gave thev same melting point of 10T-103 C.

Example 6.-A convenient method of preparing the 2,2' product wasdeveloped by taking xanthone, made from salicylic acid, and fusing itwith caustic potash (KOH) to give the 2,2'- dihydroxy-benzo-phenone;this was reduced by hydrogen using copper chromite as a catalyst, to the2,2'-dihydroxy-diphenyl-methane:

'i Hiireo...

KOH H l!(\ {il} OU UO with a melting point of 119-120 C. A mixture ofthese crystals and-the crystals (zr) above,kgave no depression of themelting point.V Numerous tests, such as making the .dimethyl ether witha melting point of 62-64 C. and the diacetate with a melting point of474'I.5 C. have proved the product to have thediortho-dihydroxy-diphenylmethane structure with a molecular weight of200; upon dehydration it yielded xanthene.

To be more specific, xanthone was made by the usual method fromsalicylic acid: to 15 grams were added 45 grams of molten KOH, and themass was heated in air at 200-230 C. The fusion was cooled, dissolved inwater and acidied with HC1. dried with a yield of 14.6 grams of2,2dihydroxy benzo-phenone soluble in alcohol; it was melted with 2.7grams of copper chromite catalyst at 175 C. and upon treatment withhydrogen at 2000 pounds pressure a pressure drop of pounds was noted,showing hydrogen absorption.

The product was dissolved in ether, 'and the catalyst `removed byfiltration; from this the phenolic portion was extracted with an alkalisolution, acidified and extracted with ether, and

The yellow precipitate was collected and decomposition.

the residue was distilled at 210 C. at 5 mm.

pressure.

The distillate on crystallization from benzene was a product melting at117.5120 C.; on dehydration it gave xanthene, thus proving itsstructure. The finally purified product melted at 119-120 C.. itsdiacetate at `4'l-4'7.75 C., the dimethyl ether at 84-84.5 C., dibenzyl1ether at 65-68 C., a bromo-derivative at 202203.5 C., and thediproplonate was liquid at room temperature.

Also xanthone was reduced to xanthene and when hydrolyzed by sodium andalcohol gave a small yield of crystals melting at 119-120 C. When mixedwith the crystals of Example 4, there was no depression of the meltingpoint.

Example 7.-The diacetate of dihydroxybenzo-phenone was produced byreaction with acetic anhydride, and the product when recrystallized fromalcohol gave an 82 yield of crystals, melting at Q-96 C. in agreementwith` the literature; the derivative is proof of the structure involved.This known product was treated with copper chromite catalyst andhydrogen at 2500 pounds pressure at 175 C. for 5 hours, dissolved inalcohol and hydrolyzed with some excess of NaOH. The alkaline solutionwas distilled free from a1cohol,` dissolved in water and acidified; andthe precipitate was crystallized from benzene to give a 25% yieldofcrystals with a melting crystals-of Example 4, there was no depressionof crystals of example 4, there was no depression of the melting point,and thus the 2,2' structure was established. Again the diethyl ether ofthe product melted at 84-84.5 C., and it did not depress the meltingpoint'of the diethyl ether `product of Example 5.

Example 8l- From a mixture of 184 grams of phenol to 80 grams (37.5%)aqueous formaldehyde, reacted for 34 hours without any added catalyst, ayield of 20 grams oi crystals, melting at 119120 C., were obtained byextraction with benzene and recrystallization. A mixture of thesecrystals with those of Example 5 had the same melting point of 119 120C.A When made into the acetate, crystals were formed meltingat 474'7.5C., and these upon adxnixture with the acetate oi.' the standard 2,2'visomer gave a mixed melting point of 47-47.5 C.

The soiubilities of the crystals produced by the foregoing Examples 5 to8 were the same, namely, 011333705000003) gram per r1.0 gram of benzeneat 25 C., i. e., they were twenty times as soluble as the 4,4' isomer.

The 2,2' isomer under alkaline conditions is.

the least stable of the isomers, and it readily changes to a resinousmass upon heating; for instance, in the presence of 3% lime by weight ofthe crystalline product, the 2,2'dihydroxydi phenyl-methane resiniledrapidly, while the 2,4' isomer was stable underthese same conditions. Itcrystallizes from water in fine needles, being slightly soluble inwater, and the crystals are very soluble in benzne, alcohol and acetone.The water-white crystals are sensitive to air-coloration in the presenceof minute traces of alkali; on heating the boiling point and meltingpoint are reduced by dehydration to xanthene and by isomerization, butat pressures below 5 mm. the product can be distilled with minor amountsof 'Ihe 2,2 isomer reacts with formaldehydeto give a heat-reactive typeof resin', and upon blending with 25% of its weight oi'hexamethylene-tetramine, the mixture rapidly heat-hardens `tol aninfusible resin. Molding compositions of constant properties can be madefrom the crystalline material, flller and hexamethylenetetramine forcharging into molds: under pressures of about 1000 pounds per squareinch such compositions have been molded within one minute at C. The pure4,4 and 2,4' crystals are also heat-hardenable when mixed with hexa orformaldehyde and useful for molding mixes and adhesives, but are lessrapid in hardening than the 2.2 crystals.

Group I isomers generally It is of interest to note that mixtures ofvthe group I isomers can be `recrystallized from many solvents Withoutany change in proportion; and in certain proportions the mixtures havesharp melting points or of such a restricted range as to lead to thefalse conclusion of the mixtures being substantially pure products. Suchconclusions apply particularly to the starred mixtures of the Resinswere made from phenol and from the class I isomer crystals by reactionwith formaldehyde and a trace of ammonia catalyst. The iinal ratio ineach case was 1 mol of phenol ring to 1.5 formaldehyde'mol, The time wastaken for the reaction of the same amount of formaldehyde as establishedby the point of infusibillty.

. Time to Relative Material 153i, speeds Minutes Phenol 73 100 2,4'isomer-.. 78 94 4,4 isomer... 66 114 2,2' isomer 9 810 a final 1.5 molsof formaldehyde using as catalyst 1 by weight of zinc oxide.

Time to i Relative Material lglai. s m is Minula Phenol 18 100 2,4isomer. 62 29 4,4 isomer. 58 32 2,2' isomer. 6 300 (Belt, 41, 323).

\ 13 The resin made from phenol had evidently gone in part through therapid 2,2 stage to arrive at a speed which, while not as rapid as pure2,2', is three times as rapid as either the'4,4' or 2,4' isomers.

GROUP II IsoMERs 2,3'dihydrozy-diphenyl-methane 15 mm. The product wasdissolved in ether and was added to an ether reaction mixture of 12.9grams magnesium and 93 grams ortho-bromanisol. The complex wasdecomposed by water and HC1, and the ether layer was distilled to give98 grams of crude'2,3'dimethoxybenzohydrol The 2,3dimethoxybenzohydrolwas oxidized with Nagenov and mso. in 'water and extracted with ether.After washing -with NaOH solution, the ether solution was distilled; theyield was 60 grams, boiling point of 218-222 C. at 12 mm. pressure; itwas demethylated with AlCl: in benzene and gave the known2,3'dihydroxybenzo phenone with melting point of 126-127 C. (this valueagrees with the literature references). The product was reduced withamalgamated zinc, and a gradual addition of HCl over 5 hrs. gave acrystalline solid that when crystallized from benzene and then fromwater gave white crystals having a melting point of 95.5-96 C. Itsdiacetate had a melting point of 43-44 C. The crystalline materialreacts rapidly with formaldehyde to give an infusible resin, no catalystbeing needed.

3,3'dihydromy-diphenyl-methane Meta-nitro-benzaldehyde was reduced tonitrobenzyl-alcohol which was condensed with nitrobenzene to obtaindimeta-dinitro-diphenylmethane. This, 1when reduced and diazotized, gavewhite crystals with a melting point of 102-103 C. that remainedconstant`on purication.

Example 10.-61 grams m-nitro-benzyl-alcohol, 183 grams nitro-benzene.1200 cc. concentrated H2SO4 were mixed and allowed to stand for 12 daysthen decomposed by ice. The precipitate was steam-distilled to free itfrom nitrobenzene, and it was then crystallized from acetic acid with ayield of 100 grams of crude 3 ,3' dinitro-dinhenyl-methane. The crystalswere reduced with iron and acetic acid. evaporated to formaldehydeeither with or without catalysts.

- 14 p and it also reacted rapidly with a mixture of phenol andformaldehyde to give infusible resins.

' 3,4'-dihydroy-diphenyZ-methane Meta-hydroxy-benzoic acid was changedto the methyl ether and this then changed to the acid chloride. The acidchloride was condensed with anisol and thus the caustic insoluble 3,4'dimethoxy-benzo-phenone was produced. This then was hydrolyzed andvreduced to the 3,4di hydroxy-diphenyl-methane and tested for molecularweight. hydroxyl content, derivatives, and constant solubility.

Example 11,- `grams of m-.hydroxy-benzoic acid was methylated withdimethyl-sulfate, using aOH in water solution, excess NaOH was then aded and the solution was boiled to hydrolize the methyl ester while themethyl ether remained stable; the yield was 100 grams ofmmethoXy-benzoic acid, melting at 107-109 C. It was treated with 330grams thionyl chloride for 24 hours vat room temperature after which theexcess was removed by vacuum distillation. The yield of the acidchloride was 110 grams boiling at 118-120 C. at 11 mm. It wasdissolvedin 65 cc. of tetrachlorethane and 85 grams anisol; theresulting complex was decomposed with ice and the excess solvent removedby steam. The product was dissolved in ether and washed with NaOHsolution; and the residue from the ether was distilled to yield 132grams boiling at 195-200 C. at 1-3 mm. When crystallized, it melted at56-57 C. and was found to be 3,4'-dimethoxybenzo phenone. This wasdemethylated with AlCla in benzene giving the knowndihydroxy-benzophenone melting at 202--203I C.

The phenone product was reduced with amalgamated zinc and dilute HC1 togive crystals melting at 1.15116.5 C. of the 3.4dihydroxydiphenyl-methane, molecular weight 20012 and hydroxyl content 17.0%; thediacetate melted at 66-67 C.

The excess solubility method used to establish the purity of suchsamples is of interest here. The sample in question was first puried byrecrystallization until it gave a molecular weight of 200:2 by' theboiling point method in acetone. Then it was checked for hydroxyl by theacetic anhydride method, using alittle pyridine catalyst to make certainit contained no material other than these isomeric dihydroxy products;it gave a hydroxyl content of 17,010.1. The crystals were recrystallizedfrom the same solvent to be used for solubility measurements, then thecrystals lwere dried to constant weight. The dried crystals weresuspended in known amounts of solvent using each time a dierentproportion of excess solid to the solvent; the solutions were 4madeslightly above 25 C. and were cooled to equilibrium at 25 C. by weighingout samples until the solubility was found constant with time.

The solutions were filtered free of excess solid crystals and the amountin solution per gram of solvent determined by driving oil.' the solventto constant weights of residue at 80-85 C. The pure 3.4' gave the samesolubility irrespective of amount of excess solid present.

What is claimed is:

1. A hydroxy-hydroxy'-diphenyl-methane having a hydroxyl on each of thephenyl rings in one of the positions ortho, meta and para to themethylene bond and characterized by a crystalline state of constantmelting point and a constam-solubility value when tested by the excesssolute method.'

2. A hydroxy-hydroxy'diphenylmethane having one hydroxyl on a phenylring in one of the positionsortho land para to the methylene bond andtheother hydroxyl in one of the ortho and para positions on the secondphenyl ring, said methane being derivable by the direct reaction of aphenol with a carbonyl organic compound selected from the class ofaldehydes, ketones and derivatives engendering aldehvdes and ketones inthe reaction. and characterized by a crystalline state of constantmelting point and a constant solubility value when tested by the excesssolute method.

3. A hydroxy-hydroxy'-diphenyl-methane having a hydroxyl on each of thephenyl rings in the position ortho to the methylene bond, said methanebeing derivable by the direct reaction of phenol with formaldehyde, andcharacterized by a crystalline state of constant melting point and a.jconstant solubility value when tested by the excess solute method.

4. 2,2hydroxy hydroxy'- diphenyl methane having a melting point of118.5`119.5 C. and reacting with 15 per cent by weight 'ofhexamethylenetetramine to an infusible gel in approximately 60 seconds.

5. 2,3'-hydroxy hydroxydiphenyl methane having a melting point of95.5-96 C. and reacting with 15 per cent by weight ofhexamethylenetetramine to an infusible gel in approximately 140 seconds.

6. 3,4'hydroxy hydroxy'- diphenyl methane having a melting point of116-1l6.5 C. and reacting with 15 per cent by weight. ofhexamethylenetetramine to an iniusible gel in approximately 130 seconds.

7. Process of obtaining in a pure form ahydroxy-hydroxy'-diphenyl-methane characterized by a hydroxyl in one ofthe positions ortho and para to the methylene bond and the otherhydroxyl in one of the ortho and para positions on the second ring whichcomprises reacting phenol sat-184,207

and formaldehyde in the presence of an acidic REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,088,677 Baekeland Mar. 3, 19141,614,171 Amann Jan. 11, 1927 OTHER REFERENCES Losev: Joun Gen. Chem, U.S; S. R., 7 pp. 1828-34 (1937), abstracted in Chem. Abst., vol. 32,column 530 (1938). l

Seebach: KunststaiIe." 27 pp. 287-90 (1937), abstracted in Chem. Abst.,vol. 32, col. 1009 (1938).

Sugimoto: Repts., Osaka Imp. Ind. Research Lab. Japan," 11 No. 2 (1930),abstracted in Chem. Abst., 25 pp. 3322-3 '(1931).

Kruber: Berichte," 74B, pp. 6193-6 (1941).

Thorps Dictionary of Applied Chemistry, 1921, vol. II, pages 431-432,the article on Crystalllzation.

Hougen and Watson: "Chemical Process Prin ciples," part one, 1943, page123.

Buhler: Joun Organic Chem," 8, 316 (1943).

4 Certicate of Correction Patent N0. 2,464,207. March 15, 1949. HOWARDL. BENDER ET AL.

It is hereby certified that errors appear in the printed specificationof the above I numbered patent requiring correction as follows:

Column 5, lines 43 and 44, in the heading to the table; fourth columnthereof, for Diethyl ther read Dethyl ether; column 11, line 31, Example7, .strike out crystals of Example 4,' there was no depression of andinsert .instead point of 118.5119.5 C'. When mwed with the;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Oce. Signed and sealed this 13th day of September, A. D. 1949.

JOE E. DANIELS, A Assiste/nt Uommzssmr of Patents.

